1. Field of the Invention
The present invention relates to a treated waste disposed of in ultra-deep underground, a method for making it and, an apparatus for making the treated waste.
2. Description of the Related Art
Recently, a method for treating waste such as a high level radioactive waste which adversely affects the environment or a human body for a long period is performed by burying or storing the wastes in the ultra-deep underground. It is important that the waste remains in the originally treated condition for a long period in order to avoid leakage and diffusion of substances to be disposed within the waste to the surroundings after disposal in the ultra-deep underground.
Therefore, a variety of procedures have been proposed and developed for stabilizing the wastes. For example, it is known from Japanese Examined Patent Publication No. 57-960 that the waste is treated by a process having the steps of filling a space portion in a container with incombustible powder, sealing the container with deaeration, and performing a hot isostatic pressing process to transform the treated waste being a block state. According to this processing method, oxidization or nitriding of the treated waste is inhibited by means of the incombustible powder so that it is possible to maintain a strong binding strength of the treated waste obtained by solidifying into theoretical density state having reduced volume for a long period of time.
Further, in Japanese Unexamined Patent Publication No. 8-20557, there is disclosed a method for producing treated waste by solidifying waste using water glasses added by a hydroxide or an oxide of an alkaline metal. In this procedure, it is possible to maintain the solidified state for a long period by maintaining an alkaline condition by means of the alkaline metal and by inhibiting the production of water of crystallization of an inorganic salt.
However, even though the treated waste stays in the originally treated condition by inhibiting oxidization or nitriding of the treated waste, or by inhibiting the production of water of crystallization, there is a problem that a substance to be disposed in the waste is ionized and transformed into an easily dissolving configuration in ground water, because the environment in the ultra-deep underground has reducing conditions due to low oxygen concentration. As a result there is a problem that the substance to be disposed in the waste leaks into the surroundings at an early stage.
As shown in FIG. 4, the environment on the ground has oxidizing conditions because of high oxygen concentration high Eh), on the other hand the enviroment in the ultra-deep underground has reducing conditions (low Eh), because its oxygen concentration is significantly lower than that on the ground.
Thus, when the waste contains the substance "I"(radioactiveiodine) to be disposed of the form of a metal compound "AgI" and exists on the ground having the oxidizing conditions, ionization of "Ag" and "I" in accordance with a reaction AgI.fwdarw.Ag.sup.+ +I.sup.- and consequent dissolution in water will be substantially avoided because of the low solubility ([Ag.sup.+ ][I.sup.- ]=10.sup.-16), even if water is brought into contact with "AgI".
On the other hand, when "AgI" exists in the ultra-deep underground where there are reducing conditions, a reducing agent causes the following reaction: EQU AgI+e.sup.-.fwdarw.Ag.sup.0 +I.sup.-
and stimulates the ionization of "I".
Although the treated waste maintains the originally treated configuration, a large amount of ionized "I" is dissolved in the ground water in the case the treated waste is penetrated by the ground water according to the following reaction: EQU 6AgI+3H.sub.2 O.fwdarw.6Ag.sup.0 +IO.sub.3.sup.- +6H.sup.+
so that "I" leaks and diffuses in the surroundings through the ground water at an early stage.